What is your transom made of?

[Jerry_NJ]

Second try, hope there is only one post:

Here I'm really talking about small boats, 2 man fishing boats.

I have owned a Grumman 14' Aluminum ProFisherman boat, purchased in about 1986. It has always had a 9.9 HP OMC 2 cycle outboard.

When this boat was damaged by the storm Sandy that hit the NE last October I purchased a 1995 Discovery 14' Voyager - also 14' Aluminum, but a deeper hull and wider by about 6".. just a bigger boat. This boat say several years of use with a 25 HP outboard I was told by the owner. I have a 9.9 HP Yamaha (circa 1990) on the boat and when tightening the engine to the transom I noticed the inside of the transum bending inward under the pressure. Looking carefully at the edges I concluded that the inside has a **** of plywood, rather thin, perhaps under 1/2" and the rest of the (didn't measure) 1" + thick transom is made up of the outside aluminum and something else. I think the Grumman is a solid piece of wood.

I put a 3/4" piece of soft wood (fir or whatever we're building homes from these days) under the clamp and it made the engine mount "feel" a lot more secure.

I'd like to put a layer of 5/4 pressure treated wood on the inside of the transom, but this makes the transom too thick to mount the Yamaha. So, I may just cut a 3/4" exterior grade plywood panel to put on the inside of the transom. I believe this will make the clamping much more secure and distribute the forces over a larger area of th existing (factory) transom.

The Discover was manufactured by a company created by some Grumman employees who left Grumman and started the Discovery company. This companay went out of business in 1996 I believe it was, and I think it was because of poor management (too rapid expansion - not enough cash flow to fund the debt), not poor quality.

Still, I am disappointed the transom isn't a solid piece of something like pressure treated 5/4" solid wood, covered by aluminum.

Another issue I have with this boat is the drain holes on the transom are too low, they are just at the water level when I am in the rear of the boat and am the only one in the boat. I go about 240 pounds. This boat is deep, uses a 20" long shaft outboard, the whole rear decking could have been raised a couple of inches and thus raised the holes a couple of inches. I looked at a 17' Discovery at a local lake yesterday and it has a higher rear deck and higher drain holes. Other than the length the two boats look identical.

I wander to some general comments about a boat no longer being manufactured, my real question/issue is the transom and appreciate what others have observed on small boat transom construction for aluminum boats.

 

[kfa4303]

Re: What is your transom made of?

Hi Jerry. When it comes to aluminum boats there are only a few rules to keep in mind. For starters, NEVER use pressure treated wood. The chemicals used to preserve the wood will react with your hull and cause pitting. Instead you'll want to use either marine grade plywood, or high quality exterior grade plywood. Most folks glue and screw two 3/4" layers together using small stainless steel screws and a construction, then seal it. Two layers of plywood properly laminated is much stronger than any solid piece of dimensional lumber you can use. You can use 2-part spreadable epxoy to seal it, which is best, but kinda pricey. You can also use several coats of Spar Urethane/Varnish which is great stuff too. If you can't find either of those, you can use several good exterior grade paint. I use Rustoleum Professional Oil Based enamel on my boat and it works quite well. You'll also want to mount the transom with stainless steel hardware dipped in 3M 5200. You can use small ss screws to fasten your decks and/or aluminum rivets as well. Aside from the epoxy, you can get everything you need at your local Lowes/HD.
As for the height of the motor, it sounds like you have a longshaft motor on a short transom. To compensate, you'll need to build/buy a small jackplate to raise the motor until the anti-vent plate, located just above the prop, is level, or slightly higher than the keel. I had to do the same job on my vintage boat and motor. Do a search here in the forums and you'll find all kinds of DIY versions, or you can buy a fancy electric/hydraulic version. Don't worry about your particular brand of boat not being made anymore. One of the best things about aluminum boat is that they're all basically the same. As long as you follow the rules I outlined above, it will last for ages.
Good luck. Holler if you get stuck.

 

[Jerry_NJ]

Re: What is your transom made of?

Thanks, I'll take a look at the engine shaft length relative to the keel. I am sure this boat requires the long shaft engine, it has a deep hull/transom. I just commented on the drain holes being low in the transom.

The engine mounts just fine, but on close inspection I found the clamps which are the usual two bolts with handles that press on the transom with what I'll estimate is a flat head that is about 1.5" in diameter - putting a lot of pressure in a small space. This is how I noticed the engine didn't pass my "shake test" but after putting a 2" by 8" or so piece of softwood under the two clamp arrangement greatly stablized the mount.

I was just lucky that the 5/4 pressure treated would have been used, however, the bulk of that wood would be pressing on the transom plywood, not the aluminum.

I just thought the whole transom looked/felt flimsy - but this boat is about 20 years old and the transom is still there and functioning. It could be me... I'll take a closer look tomorrow and a closer look too at the damaged Grumman boat the Discovery was purchased to replace.

Another learning experience for me is setting the proper trim on the engine. I'll estimate the transom angles backwards at about 15 to 20 degrees and I have the engine trimmed so that the drive shaft is almost perpendicular with the keel. Using only a 9.9 HP the engine seems to "plow along" with a churn out the back, not the "V" wave I used to get on my Grumman using a 9.9 HP OMC engine (have had both Johnson and Evinrude). I attribute it to the Discovery being heavier, so the engine is pushing more and thus can't get the "rooster tail" formation. Keep in mind I'm talking 14" boats with about 400 pounds of load, most in the rear. I think too the bow rides a little high, but bringing the trim in (bringing the engine drive shaft more parallel to the transom) doesn't bring the bow down enough for me to notice. I believe bringing the prop closer to the transom pushing more up on the stern, bringing the bow down. I don't find this boat to be very sensitive over the few degrees of adjustment this engine (Yamaha 1990) has.

Still, overall, I like the boat and when on a lake a few days back with the wind coming up the deeper hull have the boat a more secure feeling even though I was moving slower than I am used to with the Grumman.

 

[kfa4303]

Re: What is your transom made of?

Here's a handy pic on dialing in the tilt/trim. It mostly just takes trial and error, but most folks find the 2-3 pin position away from the transom works best. Using a tiller extender will allow you to move your weight forward as needed to help get on plane. I use on on my boat and it makes a huge difference. You can sit, stand, or move around as you like and still control the motor. I made mine of out PVC, but there are fancy carbon fiber/aluminum versions as well. You may also want to look into adding some trim tabs/pods.

 

[Jerry_NJ]

Re: What is your transom made of?

Thanks, I think my "trim" is about as in your picture.

I have noticed, even at Walmart the outboard handle extension and have been thinking about buying one for when I want to make better time. I also wondered about he fins mounted on the anti-cavitation plan and while I see them listed for small HP engines I wondered how they would help, maybe the churn I describe in the rear at full throttle is cavitation.. never tried to understand that term.

At 9.9 HP I don't hope to get the hull on a plane (isn't that when the boat is touching the water only with the rear 1/3 or so of the hull?) but I would like to get the top speed up a couple of mph.

 

[loose rivet]

Re: What is your transom made of?

What is the layout of your new boat, could there be some wet flotation foam in that hull making it stern heavy?
It sounds like its riding pretty low if the splashwell drains are at the water line or lower.
Most boats that size don't draw much water with only a 240lb man at the tiller.

I run a 14.5' Grumman SSV, with my 300lbs at the tiller, a 124lb motor, battery and 3 gallon fuel tank all in the stern, it doesn't come near taking on water over even its 15" transom. It does plane easier with more weight forward though. If out by myself I usually carry a spare 6 gallon fuel tank in the bow. A 9.9 will plane the boat but barely. A 15hp is in my opinion the smallest motor for the hull to reliably get on plane.

If the transom wood is suspect, it needs to be replaced, its not a big project and the transom is the most important structural part of your boat.

I do remember there being some issue with a few model years of Discovery boats where they used the wrong plywood or glue and it was eating the aluminum. It may be best to remove the factory wood and redo the transom just to be safe. Otherwise they were good boats. Those with full floors had foam flotation, like many other boats, which absorbs water over years of use, more so if stored outdoors uncovered.

 

[Jerry_NJ]

Re: What is your transom made of?

I doubt there is water on board, but it is very heavy. In truth the years have also piled up on me so I'm not as strong as I once was. I know when trying to move the stern over an inch or two after loading (bunks still wet) I can't.. not even budge the stern. My Grumman with the 15" transom and 6" narrower took my full output to move it such a distance, but I could. I am now moving my trailer loading rods (a vertical double roller) from the Grumman trailer to the Discovery. This should help load the boat on center, especially when some wind exists.

The Discovery is heavy enough I have started launching the right way; tying the bow line to my truck then pulling the trailer out from under the boat - nice too my shoes stay dry. I just wore "water shoes" and man handled my Grumman off the trailer, backing just enough to have the stern in the water. Both trailers have 12" tires, so it takes putting the truck rear wheel in the water to launch by pulling the trailer from under the boat.

I have another Discovery to compare with, it is a 17' (owner who weights I'll guess 20 pounds more than me) mine a 14'. His transom drain holes are at least 3" higher than mine. I could see his waterline mark and the holes were about 3" above that line. suggesting my drain holes are too low. Still my boat's drains are above the water line, and water splashes in from mild wave action when sitting still. The hole on the other side doesn't take on any water under the same condition - just the side I'm sitting on. I have two deep cycle batteries in the rear, about a foot forward of the transom, one battery is a 100 AH the other a 70 AH, I'll estimate total weight being in the 100+ pound range. My 3 gallon gas tank is mid-ship and on the same side as I sit. I can see the bottom of the hull behind the batteries as the flooring stops exposing the aluminum hull back under the rear cover shelf. It has a bulge pump but has not yet taken on enough water to pump.

The boat has been and is stored outside, but it has a quality cover and this winter I'll double that with a cheap overlay tarp. The elevated seats, including a "bass boat" type seat on the front elevated deck nicely raise the cover so that the water can run off. Looks like it has a center windshield under the cover. But, when for sale the owner had it open in the yard and we had some set snow during that time. We were still negotiating price but I asked him to cover the boat anyway... this was in late November, he wasn't getting a lot of "lookers" so I had that going for my side of the negotiation.

Anyway, I put some aluminum colored duct tape over the holes...and I am considering using an engine control/steer extension to move forward when operating.. and fishing as I have not yet put on a bow electric motor. The front deck was my preferred fishing spot on my Grumman, and I have removed my home made bow motor mount from the Grumman, it looks like it will fit well on the Discovery.

The Admiral suggested using a piece of PVC pipe for a motor control extension, and I will guess duct tape : ) I may try that first before spending some $25 or so on a factory made extension. Unfortunately the next position forward (seated) is the built-in storage chest, the stern seat is a nice padded deck chair on the rear "bench".

Overall the Discovery is in very good condition, even has one original seat which I have mounted on the front bass boat seat position. This seat must have been in storage as it still has a nice Discovery label on it, not cracked looks good for another 20 years. The other two seats are recent Cabela mid-priced seats and the trailer has new wheels and tires. The trailer lights, that's another matter, I replaced them with the rectangular style that are a bit better keeping water out that the older style square shape lights (Peterson lights). Then broke one on the RH side when loading the boat. I hope the loading rails I am installing will prevent that in the future. I've looked at the newer LED lights and they seem to be fully sealed, water proof, but I'm putting off spending the $50 as I had the subject replacements on hand, and I am still stripping the Grumman trailer for parts.

I believe the Discovery is enough bigger and deeper to be more sea worthy and comfortable if more than I am on board (my wife's health doesn't make her interested in coming along as she used to), but for just me I like the smaller Grumman better. Too bad "Super Storm Sandy" dumped some large White Pine trees on the little friend - I purchased the Grumman new in 1986, date from memory. The Discovery joined my family in November 2012.

 

[Jerry_NJ]

Re: What is your transom made of?

Administration question. On my recent long winded replies I have fond the iboat site rejects my attempt to post the message. Maybe some time-out is taking place. Being careful I copy my message, then "refresh" and log in again. The past work is lost in the process, but I have a copy so I paste it in my second attempt. When I then request my reply be posted, it goes forward immediately. I also notice my message construction is being auto saved, how do I access that if I have not made a backup copy myself?

Maybe there is a parameter I can set that gives me more time to type, and proof read, that's what takes time

 

[jigngrub]

Re: What is your transom made of?

I doubt there is water on board, but it is very heavy.

A "heavy" boat and rotten transom = saturated floatation. Saturated floatation can/will add hundreds of pounds to your boat and slow it down. It'll also make your boat set lower in the water as you described above. Saturated floatation is also a safety hazard, it has lost it's buoyancy and will not float your boat in case of an emergency, your boat will sink to the bottom.

Saturated floatation is a common problem we see all of the time in the restoration section of this forum. It's not a hard job to fix and you'll be amazed at how much better your boat will perform with new dry floatation.

 

[Jerry_NJ]

Re: What is your transom made of?

Thanks, can you point to a thread on replacing/repairing transom flotation? Here I assume there is flotation behind the transom inside "wall"... that would explain the "soft" plywood in the inter side.

How about just drying out the existing flotation, It can't permanently hole water, can it? I will use a mirror to look up at the tansom from below. I am of the impression the Gumman has a solid transom. The Discovery boat (current subject) has two compartments on either side, must be (I can measure) 1.5' long by 1' deep by 1.5' high full of flotation. That would be approximately 4.5 cu feet of flotation in the two sides...that's a good bit of flotation even if none is inside the transom.

Maybe with luck someone here knows how the Discovery transom is constructed.

 

[jigngrub]

Re: What is your transom made of?

No floatation in or behind the transom, the transom is soft because of wood rot.

Boats with wood rot more times than not have saturated floatation as well because of exposure to the elements.

The 2 compartments you speak of have contributed to your transom rot by holding moisture up against the transom. Dig the foam out and you will find it wet, you'll also find the transom wet in that area too.

All the foam in your boat should be checked for moisture.

 

[Jerry_NJ]

Re: What is your transom made of?

I did a quick finger test and look over the transom on the Grumman. It has what feels like two layers of 3/4" wood, bet it is plywood. This doesn't come all the say down to the hull, stopping about 8" above the hull, and any water that is in the bottom of the boat... I'd say there is no flotation in the transom. I'll check further on the Discovery.

I have been in one of the side compartments on the discovery to fish a wire up from the sonar transmitter/antenna. It was not wet as far as that experience goes.

One question in my mnd, why make flotation out of a material that absorbs water, isn't that doomed to fail? Even wood drys out if kept away from water.

Still, my Discover does ride low in the stern, but as said a similar Discover has the drain holes higher up and it too would take in water splashes if the holes were as low as on my boat.

 

[jigngrub]

Re: What is your transom made of?

2 pieces of 3/4" plywood laminated/bonded together is pretty much standard for the vast majority of boat transoms.

Transom wood gets wet a number of ways, mainly exposure to the elements (rain, smow, and ice) and improperly sealed penetrations in the transom like motor mounting bolts and other holes for nuts screws and bolts. When the side of the transom wood against the hull gets wet it'll never dry out, we see this nearly every day in the restoration forum. And if the water stays trapped too long it depletes of oxygen and turns acidic and corrosive and cam cause some very nasty corrosive pitting in the aluminum on the transom wall against the wood, this is very common too.

Todays 2 part expanding urethane floatation foam is very water resistant and will last a very long time if the boat is properly cared for, this means covered when not in use with the drain plug out. Unfortunately the majority of people don't do this, they don't cover the boat and either leave the drain plug in because they don't want to forget it the next time they go out... or they pull the plug but don't cover the boat and it fills up with leaves and plugs the drain hole up and holds water. When constantly exposed to water, the expanding foam wiil start to absorb the water... but even this takes a long time. Here's a quote about how long it takes the foam to become saturated:

14. Is this foam water resistant?

Yes, but with the following caveat. The foams that we sell are considered closed-cell, which means that each cell that makes up the foam structure is completely closed off from surrounding cells which prevents it from acting like a sponge. It is completely safe for this foam to be in contact with water for hours/days/weeks and even months with no adverse effects. However, it should never be submerged in contact with water permanently. Over a period of years the water contact can begin to soften the foam and cause it to lose its closed-cell status. This foam is designed primarily to be used as an insurance policy in case of damage/holes that could cause a vessel to lose buoyancy. Pinhole sized openings would essentially have no effect on the foam since the amount of exposure is so minimal but you should always make repairs as soon as possible to keep the foam effectiveness as good as possible. This will be the case with all after market closed-cell polyurethane foams and even manufacturer installed foams.

... and that is from here:
Frequently Asked Questions - General

People think "It's a boat, it was made to get wet!"... and yes, it was made to get wet. But it wasn't made to stay wet, boats need time to dry out and the owner needs to do all they can to help speed the drying time.

I have a 16 nyr. old Tracker tinny I bought new back in '97, all of the wood is original and in mint shape and the foam is original and bone dry. The boat has always been kept outdoors, but covered with the drain plug out. Any water that happens to find it's way in if the cover leaks or blows off drains right out through the transom drain. I don't have any leaks in my hull, when I pull the plug after a day on the water a little bit of dust falls off of the end of the plug.

Go to the restoration forum and read the horror stories of what happens when people neglect their boats and leave them exposed to the elements and water intrusion.
Boat Restoration, Building, and Hull Repair

You'll also learn a lot about how boats are put together and what it takes to fix them when they go bad.

 

[Watermann]

Re: What is your transom made of?

Jerry the above posters to your thread have heard your story 100's of times and I know most guys want there to be an easy fix but there really isn't. You will either need to make the needed repairs that are suggested or keep using your boat in an unsafe condition. Take a look at your decking, has it been doubled up over the top of the old? That adds a lot of weight too. Boats made in the 90's should all have foam flotation that can and will water log. No it won't ever dry out again, it has to be removed and replaced if water logged. You will have to do a thorough inspection of the boats flooring, foam flotation and transom wood. If any of it is rotten or water logged then your in for a rebuild.

The splashwell drains should not be covered up or plugged, if a wake or wave comes over the transom there isn't any way for the water to exit the slashwell and will contribute to a swamped boat. What ever water washes into the splashwell through the drain tubes will go right back out again. I have what should be a considerably heavier boat in my 16' with 55 OB, battery, full livewell, fuel tank with a 200 LB fishing buddy in back and have been in rough water with 3 foot waves. The boat rides right up over them and no water even comes over the transom into the splaswell. It really sounds to me like your boat is way heavier than it should be. You can also go and weigh the boat on a scale to see if your looking at increased weight due to water logged foam.

What is the distance measured from the center of the transom from the bottom to the top and at what point in the measurement are the drain tubes located?

 

[Jerry_NJ]

Re: What is your transom made of?

The boat has never in my use ever come close to taking water over the transom into the splash well. What I see is normal wave action will splash into the drain hole into the splash well. This makes the carpet wet near the hole, and is only a small portion of the splash well that gets wet. The hole on the opposite side (port) doesn't take in any water. This also happens only when sitting with no power on, just drifting (no anchor either). The Discovery has a 20" stern.

I measured the distance vertically from the drain hole to the bottom of the hull (not the keel, but directly under the holes which are about 18" from the center). The holes are about 1.25 inches in diameter and the top is about 12" above the bottom of the boat. Strangely I find the same distance on the Grumman which has a 15" stern. The Discovery company was started by some Grumman expatriates (I'll call them) and it may be they made the Discovery Voyager as a step up competitor to the Grumman Pro Fisherman I have. The Discovery, as said is bigger, wider and taller/deeper...but the same length. Other differences I note include the older Grumman has a more elaborate hull at the place where the bottom (what's that called?) meets the side of the boat. The Discovery has a simply joint, the Grumman has a splash guard (I'll call it) that begins at that stern and runs all the way to the bow.. this looks to be more sophisticated that the Discovery (a few years newer), I wonder if it was determined the extra on the Grumman didn't add any value or worse made the hull perform worse - if this subject has any interest I can take a picture and post it.

Another difference I just noted that added to my feeling the Discovery is much heavier. The trailer (both are Shorelander) on the Grumman is much longer. Both boats are 14' in length and the Grumman trailer measured over 3.5' from the bow to the trailer hitch ball... the discovery is under 2' in length, giving me a lot shorter lever when lifting at the hitch, also when launching the Grumman was deeper in the water for the same truck position. I typically didn't put the rear wheels of my truck in the water with the Grumman - this just didn't work with the Discovery.

I'll look again, but I can say that the compartments that hold flotation on the two sides at the stern do not extend to the bottom of the boat so water in the bulge doesn't reach the flotation material unless it is over about 8" deep, up over the wood/carpet floor.

I will spend some time tonight studying the reference materials pointed to by "jugngrub", thanks.

 

[Watermann]

Re: What is your transom made of?

Just to give you an idea, my 16'er's transom is 20" high and the drain tubes for the spashwell are 5" below the top of the transom or 15" from the bottom. So yours are 12" above the bottom of the hull for a 14' boat with a 15" high transom making them 3" below the top.

Sounds about right to me. I don't see how your boat could have that much weight from just a person and small OB to displace 12" of hull under water causing the drain tubes to take on lake water. That is just not normal, you have some extra weight in the stern and your bow must just about be impossible to see over when under way.

 

[Jerry_NJ]

Re: What is your transom made of?

I must have used too many word, too few facts.

Subject 14' Discovery has a 20" transom, the drain holes are about 10" above the bottom (measured vertically, not against the low point of the keel) and the holes are 1" in diameter, and are thus 9" down from the top of the transom.

I gave a comparison to my 14' damaged Grumman with a 15" transom as both boats have the drain holes up only about 10". The Grumman did not have water splash in through the drain holes, must have ridden higher in the water at the stern.

 

[jigngrub]

Re: What is your transom made of?

I must have used too many word, too few facts.

Subject 14' Discovery has a 20" transom, the drain holes are about 10" above the bottom (measured vertically, not against the low point of the keel) and the holes are 1" in diameter, and are thus 9" down from the top of the transom.

I gave a comparison to my 14' damaged Grumman with a 15" transom as both boats have the drain holes up only about 10". Still, rs, ever had water splash in through the drain holes.

1 picture is worth 1,000 words.

 

[agallant80]

Re: What is your transom made of?

I have a bayliner so I am assuming horse hair and old news papers covered with plaster.....

 

[Watermann]

Re: What is your transom made of?

I have a bayliner so I am assuming horse hair and old news papers covered with plaster.....

:laugh:

Jerry the problem also might be posting about 2 boats at the same time. Maybe limit the dimensions and talk to just the boat with the problems.